Systems and methods for reducing the energy requirements of a carbon dioxide capture plant

ABSTRACT

Systems and methods for reducing the energy requirements for carbon dioxide capture are described. Heat from system processes, such as steam condensation and hot flue gas, is utilized to heat reflux liquid utilized in release of carbon dioxide from absorbent solvent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority benefit under 35U.S.C. §121 to co-pending U.S. patent application Ser. No. 13/737,804,filed on Jan. 9, 2013, and entitled “Systems and Methods for Reducingthe Energy Requirements of a Carbon Dioxide Capture Plant,” which ishereby incorporated by reference for all purposes as if reproduced inits entirety.

FIELD OF THE INVENTION

The field of the invention is systems and methods for capturing carbondioxide.

BACKGROUND

Despite the growing availability of alternative energy sources, theenergy needs of most of the world are primarily met by the combustion offossil fuels such as coal, oil, and natural gas. Among other byproducts,such combustion produces carbon dioxide (CO₂), the release of which intothe environment is becoming increasingly regulated. CO₂ emissions may bemitigated, at least in part, by capturing CO₂ directly from largesources of emissions, such as generating plants that combust fossilfuels as a power source. Rather than simply venting CO₂ into theatmosphere, CO₂ can be removed from flue gases using a CO₂ absorber. Thecaptured CO₂ may then be utilized in other processes or sequestered.Similar capture methods can also be applied to other industrialprocesses that generate significant amounts of CO₂ including, forexample, ammonia production, fermentation processes, removal of CO₂ fromnatural gas or biofuel products, and so forth.

CO₂ is generally separated from a gas mixture by absorption. The fluegas, for example, may be a flue gas generated by a boiler that producessteam for a power plant. In a typical process the gas mixture is passedthrough an absorption column where the gas is exposed to a capturemedium that absorbs some or all of the CO₂ component of the mixture.Typically, this absorbent is in a liquid phase and is often an aqueoussolvent that contains one or more amine compounds. Such a process issometimes referred to as wet scrubbing. The gas mixture is passedthrough the absorption solution at pressure and temperature conditionsthat permit absorption of substantially all the CO₂ into the absorptionsolvent. The CO₂-lean gas mixture emerges at the top of the absorptioncolumn and may be directed for further processing as necessary. Theabsorption solvent, which is now rich in CO₂ (i.e. a rich solvent),exits from the bottom of the absorption column, and is then subjected toa stripping process to remove the CO₂ and regenerate an absorptionsolvent that is lean in CO₂ (i.e. a lean solvent).

Regeneration of the lean solvent typically involves heating the richsolvent to reduce the solubility of CO₂. To ensure complete or nearcomplete removal of CO₂, the rich solvent may undergo successive cyclesof reheating. In a typical solvent regeneration process, rich solvent isintroduced into a regeneration column at a high temperature. Thiselevated temperature is maintained by a reboiler. At these elevatedtemperatures, the rich solvent releases absorbed CO₂. The regeneratedlean solvent may be collected from the bottom of the regeneration columnfor reuse in the absorption column, while a gas phase containing thestripped CO₂ (along with water) is collected from the top of theregeneration column. This gas phase may be passed through a condensersystem that condenses water vapor and returns the liquid to theregeneration column. The released CO₂ may then be collected forreutilization or sequestration.

As noted above, the energy requirements for existing absorption andrecovery processes can be significant, in large part due to the heatrequired for stripping CO₂ from the rich solvent. Because this heat istypically derived from steam that would otherwise be used for powerproduction, the heat requirements of the reboiler can reduce net powerproduction. Attempts have been made to reduce this burden by redirectingheat from other plant processes. For example, U.S. Pat. No. 5,344,627(to Fujii et al) discusses discharging steam from a high pressureturbine and directing it to an auxiliary turbine that powers acompressor used to liquefy recovered CO₂. The steam discharge of thisauxiliary turbine provides heat for a reboiler. In WIPO publ. no.WO2011/073671, Hume and Kuczynska describe a similar approach in whichsteam discharged from a high pressure turbine is utilized to drive aback pressure turbine, which in turn drives a compressor used tocompress CO₂ recovered from the rich solvent. This compression producesheat, which along with heat from the exhaust of the back pressureturbine, is supplied to the reboiler. However, since the discharge fromhigh pressure turbines is typically utilized in lower pressure turbinesto generate additional power, these approaches still directly impactpower generation.

A similar approach is described in U.S. pat. publ. no. 2010/0050637 (toYamashita et al), which discloses diverting a portion of the steam inputto a low pressure turbine to drive an auxiliary turbine, and utilizingthe steam exhaust from this auxiliary turbine as a heat source for areboiler. Since this directly impacts the power output of the lowpressure turbine, however, power generation is still impacted. Analternative approach is disclosed in U.S. pat. publ. no. 2010/0050637(to Yamashita et al), where a reboiler is supplied with heat via aheating medium, which is in turn receives heat from the flue thattransports the initial waste gases via a heat exchanger. It is, however,unclear if such a source can provide sufficient heat at the propertemperature for the needs of the reboiler.

These and all other extrinsic materials discussed herein areincorporated by reference in their entirety. Where a definition or useof a term in an incorporated reference is inconsistent or contrary tothe definition of that term provided herein, the definition of that termprovided herein applies and the definition of that term in the referencedoes not apply.

Unless the context dictates the contrary, all ranges set forth hereinshould be interpreted as being inclusive of their endpoints, andopen-ended ranges should be interpreted to include commerciallypractical values. Similarly, all lists of values should be considered asinclusive of intermediate values unless the context indicates thecontrary.

Thus, there is still a need for systems and methods that reduce theenergy requirements for regeneration of solvents used in CO₂ capturefrom flue gases, particularly in power generation plants that rely onfossil fuel combustion.

SUMMARY OF THE INVENTION

The inventive subject matter provides apparatus, systems and methods inwhich one can remove CO₂ from flue gases using a solvent system andregenerate solvent in an energy efficient manner, in an embodiment ofthe inventive concept, a boiler heated by fossil fuel combustiongenerates steam that may be used for power generation, and in thisprocess generates hot flue gas containing CO₂. CO₂ can be captured fromthis flue gas in a CO₂ capture unit that utilizes a solvent, whichabsorbs CO₂ and thereby generates a rich solvent. This rich solvent isdirected to a stripper, where it typically moves against stripping steamin a counterflow fashion. Such flow releases at least a portion of theCO₂ from the rich solvent to generate a semi-lean solvent, which exitsfrom a lower portion of the stripper. All or a portion of the semi-leansolvent can be directed to a reboiler, where it is heated with lowpressure steam. At least a portion of this steam condenses in thisprocess to release heat to the semi-lean solvent via a phase change. Aportion of the semi-lean solvent vaporizes to form a 2-phase mixture.This 2-phase mixture is returned to the stripper, where the vapor phasejoins the stripping steam that flows up through the stripper. The liquidphase exits from a bottom portion of the stripper as a lean solvent;this lean solvent is in turn directed to a CO₂ capture unit.

Stripping steam carrying released CO₂ exits from a top portion of thestripper as a CO₂ saturated stream. The CO₂ saturated stream is carriedto a condenser where a majority of the water can be condensed to aliquid to generate a process condensate. CO₂ is subsequently separatedfrom the process condensate in an overhead accumulator. From theoverhead accumulator, the process condensate may be directed to variouspaths. For example, a portion of the process condensate may be returnedto the upper portion of the stripper as reflux. Another portion of theprocess condensate may be directed to a reflux heater, where heat fromthe hot flue gas may be used to generate steam that is routed to thestripper for use as stripping steam. Yet another portion of the processcondensate may be directed for use in various plant processes. In someembodiments of the inventive concept the condensate from the lowpressure steam utilized to heat the reboiler can be used as a heatsource in the reflux heater, which produces a sub-cooled steamcondensate, thereby lowering the net steam requirement of the CO₂capture plant.

One embodiment of the inventive concept is a system for reducing theenergy requirements of a CO₂ capture process in a plant, where thesystem includes a stripper that receives a rich solvent stream, steam,and a reflux stream, and produces a lean solvent and an upper productthat includes CO₂. Such a system may include a condenser that receivesthe upper product and produces a condensed stream, and a heat exchangerthat receives at least a portion of the condensed stream. The heatexchanger can be arranged to transfer heat between a heat exchangemedium and a portion of the condensed stream to produce steam. In someembodiments of the inventive concept, the heat exchanger may receive aportion of the condensed stream, and the reflux stream includes anotherportion of the condensed stream. In other embodiments of the inventiveconcept, the system also includes an accumulator that receives a portionof the condensed stream, and produces a CO₂ product stream and acondensate stream. This condensate stream may form at least a part ofthe condensed stream that is received by the heat exchanger. The heatexchange medium can be a flue gas stream and/or a reboiler condensate.In such an embodiment, the stripper may have a fluid connection to areboiler, which may allow for an exchange of heat between a solventstream of the stripper and a second heat exchange medium. This heatexchange may produce a reboiler stream and a reboiler condensate.

Another embodiment of the inventive concept is a system for reducing theenergy requirements of a CO₂ capture process, which includes a stripperthat receives a rich solvent and a reflux stream and produces an upperproduct that includes CO₂. Such a system may include a condenser thatproduces a condensed stream from at least a portion of this upperproduct, and may also include an accumulator that receives the condensedstream and produces a condensate stream. At least part of thiscondensate stream may be returned to the stripper as a reflux stream.Part of the condensate stream may also be directed to a heat exchanger,where heat transfer between the condensate stream and a heat exchangemedium produces steam. A portion of this steam may be directed to thestripper. In such an embodiment, the heat exchange medium can be a fluegas stream and/or a reboiler condensate. In some embodiments of theinventive concept, the stripper may be in fluid communication with areboiler, which may permit heat exchange between a solvent stream fromthe stripper and a second heat exchange medium, thereby producingreboiler steam and/or reboiler condensate.

Yet another embodiment of the inventive concept is a method for reducingenergy requirements in a CO₂ capture process. Preferred methods includethe steps of producing a condensed stream from at least part of an upperproduct stream of a stripper (which may include CO₂) by condensation anddirecting at least part of this condensed stream to the stripper as areflux stream. Such methods may also include exchanging heat between aportion of the condensed stream and a heat transfer medium in a heatexchanger to produce steam; this steam may in turn be directed to thestripper. This heat transfer medium can be, for example, a flue gas froman upstream component such as a boiler. Alternatively, the heat transfermedium can be a reboiler condensate. In other embodiments, at least aportion of the solvent stream may be directed from the stripper andutilized to cool a second heat transfer medium using a heat exchanger.In such an embodiment the second heat transfer medium can be a reboilercondensate. At least a portion of the condensed stream may be separatedinto a CO₂ product stream and a condensate stream. In some embodimentsthe condensed stream may include, at least in part, a portion of thecondensate stream.

Various objects, features, aspects and advantages of the inventivesubject matter will become more apparent from the following detaileddescription of preferred embodiments, along with the accompanyingdrawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of one embodiment of the inventive concept, inwhich heat from flue gas is utilized to heat reflux that is returned toa stripper.

FIG. 2 is a schematic of another embodiment of the inventive concept, inwhich heat from condensed low pressure steam is utilized to heat refluxthat is returned to a stripper.

FIG. 3 illustrates a method of the inventive concept, in which a productfrom a stripper is treated for return to the stripper.

FIG. 4 illustrates a method of the inventive concept in which a productfrom a stripper is treated with heat from a second product of thestripper for return to the stripper.

DETAILED DESCRIPTION

It should be noted that while the following description is drawn tosystems and methods for improving the energy efficiency of recoveringCO₂ from flue gases, various alternative configurations are also deemedsuitable and may be employed to treat any suitable source of CO₂containing gas streams, such as streams from combustion processes in theoil and gas industry, cement plants, lime kiln exhausts, engineexhausts, fermentation processes, hydrogen production plants, ammoniaproduction plants, processing of phosphates, and so forth. One shouldappreciate that compounds other than CO₂ may be recovered, including(but not limited to) CO, ammonia, nitrogen oxides, sulfur oxides,volatile organic carbon compounds, and chlorofluorocarbons, from gasstreams containing such compounds.

One should also appreciate that the disclosed techniques provide manyadvantageous technical effects including reduction in the application ofhigh temperature heat to solvents utilized in CO₂ recovery (therebyminimizing their degradation), reduction of water consumption in the CO₂recovery process by generating stripping steam utilized for solventrecovery from process water, and reduction of the temperature of fluegases prior to CO₂ capture, thereby reducing the need for active coolingof flue gas prior to entering a CO₂ capture unit.

The following discussion provides many example embodiments of theinventive subject matter. Although each embodiment represents a singlecombination of inventive elements, the inventive subject matter isconsidered to include all possible combinations of the disclosedelements. Thus if one embodiment comprises elements A, B, and C, and asecond embodiment comprises elements B and D, then the inventive subjectmatter is also considered to include other remaining combinations of A,B, C, or D, even if not explicitly disclosed.

The inventive subject matter provides apparatus, systems and methods inwhich one can remove CO₂ from flue gases using a solvent system andregenerate the CO₂ capture solvent in an energy efficient manner. In oneembodiment of the inventive concept, a boiler heated by fossil fuelcombustion generates steam that may be used for power generation, forexample by providing high pressure steam that is directed through aseries of turbines used to generate electric power. It is contemplated,however, that systems and methods of the inventive concept may also beapplied to combustion processes utilized in the coal, gas, and/orpetroleum industries (such as, for example, from a reformer furnace, agas turbine, a water heater, a steam generator, a reboiler, and aliquefied natural gas heater).

Such processes generate hot flue gas that contains CO₂, release of whichinto the atmosphere is being increasingly regulated. Therefore, there isconsiderable interest in the removal of CO₂ from such flue gas prior tobeing exhausted to the atmosphere; the CO₂ may then be utilized in otherprocesses or sequestered to prevent environmental release. CO₂ may becaptured from flue gas in a CO₂ capture unit. Typically, such devicesprovide contact between the flue gas and an absorptive media thatsolvates or otherwise capture CO₂. Typical liquid absorptive solventsinclude amines or similar compounds, often admixed with water. However,any commercially suitable solvent could be used. Uptake of CO₂ by such asolvent generates a rich solvent (i.e. a solvent rich in CO₂). For peakefficiency, such processes should be optimized for temperature andpressure that provides optimal CO₂ uptake by the solvent, which oftenrequires cooling the hot flue gas from combustion processes (for exampleusing refrigerated contact coolers) to bring the flue gas to optimaltemperature.

Following absorption of CO₂ from flue gases, CO₂ is removed from therich solvent using a stripper. Temperature and pressure conditionswithin the stripper decrease the solubility of CO₂ in the solvent;typically, the temperature of the absorptive solvent is increased inorder to release the absorbed gas. In addition, strippers generallyinclude internal packing or similar structure to increase surface areaand expose more solvent to the internal atmosphere. Heat may be providedin the form of steam, which may be introduced through a lower portion ofthe stripper so that steam and solvent interact in a counterflowfashion. The resulting lean solvent may be collected from the lower partof the stripper (from where it may be returned for use in a CO₂ captureunit) while the released CO₂ can be collected from the upper portion. Inpractical terms it is often necessary to pass the solvent through thestripper repeatedly in order to remove all (or essentially all) of theabsorbed CO₂, so solvent is typically refluxed through the stripper.

The process of removing CO₂ from the rich solvent therefore requiresconsiderable heat energy, which is supplied to the solvent, at least inpart, by a reboiler that is in fluid communication with the stripper. Asnoted above, it is a common practice to utilize a portion of the steamthat is produced by a fossil fuel driven boiler to provide this heat,however this practice directly impacts the efficiency of the plant.Systems and methods of the inventive concept utilize heat energyproduced by system processes to alternatively provide heat for thereboiler and thereby improve plant efficiency.

One embodiment of the inventive concept is shown in FIG. 1. Rich solvent(100) from a CO₂ capture unit (not shown) is directed to a stripper(105). A semi-lean solvent (110) is collected from a point below thepacking and directed to a reboiler (120), where it is heated. Heatenergy is preferably supplied to the reboiler (120) in the form of lowpressure steam (130), although any commercially suitable heat exchangemedia could be used. Such steam may, for example, be collected from theexhaust of a turbine. Examples of suitable turbines include, forexample, a low pressure turbine from a series of high, mid, and lowpressure turbines utilized for power generation and a turbine used topower a compressor. Utilization of such sources of low pressure steamalso advantageously minimizes the impact on power generation. Inaddition, the use of steam raised from process water advantageouslymaintains the water balance of the plant by eliminating the need toinject water from an outside source into the system.

At least a portion of the low pressure steam condenses in this process,generating a reboiler condensate (135), and transferring the resultingheat of condensation from the condensing steam to the solvent.Utilization of this phase change for energy transfer advantageouslyreduces exposure of the solvent to high temperatures, such as those thatare experienced when solvent is heated using high pressure steam, whichminimizes degradation of the solvent. This results in vaporization of aportion of the semi-lean solvent, and the resulting two phase solvent(125) is returned to the stripper (105). This releases stripping steamwithin the stripper (105), where the substantially CO₂ free lean solvent(140) is removed from a lower portion of the stripper (105) and may bedirected to a CO₂ capture unit. In some embodiments of the inventiveconcept the lean solvent (140) is removed from the bottom of thestripper (105). Stripping steam rises through the stripper (105),carrying released CO₂ through the upper part of the stripper (105) as aCO₂ saturated stream (145). It is contemplated that CO₂ may be releasedfrom other components of the CO₂ saturated stream (145) by cooling in acondenser (150), and subsequently separated from liquid components in anaccumulator (165). In typical overhead accumulator (165) configurations,product CO₂ (155) is collected from an upper portion and productcondensate (160) is collected from a lower portion. This condensate(160) may be primarily water, but may include amines or other compoundsutilized in the capture of CO₂.

Condensate (160) may be distributed to one or more destinationprocesses, optionally with the aid of a pump (167). Embodiments of theinventive concept may include one or more valves and/or pump(s) and anassociated controller that permits control of the distribution of thecondensate (160) in order to optimize plant operations. It iscontemplated that condensate (160) may be directed to two or moredestination processes and/locations simultaneously. In some embodimentsof the inventive concept, at least a portion of the condensate (160) canbe directed to the stripper (105) as reflux (170). In other embodimentsof the inventive concept, at least a portion of the condensate (175) canbe directed to other parts of the plant. In still other embodiments ofthe inventive process, at least a portion of the condensate (180) can bedirected to a reflux heater (185).

A reflux heater (185) may be used to heat the condensate (160) togenerate steam (190) utilizing heat from a suitable source. Suitablesources include, for example, hot flue gas (195) and a reboilercondensate and may be transferred to the condensate (160) via a heatexchanger. Where the source is a flue gas, the flue gas may, forexample, originate in a boiler utilized to generate steam for powergeneration, but may alternatively be obtained from other combustionsources such as a burner, a reformer furnace, a gas turbine, a waterheater, a steam generator, a reboiler, and/or a liquefied natural gasheater. It is contemplated that one or more flue gas sources may becombined to provide a pooled flue gas source for the reflux heater(185). This process reduces the temperature of the flue gas to produce acooled flue gas (197), which may be routed to other parts of the CO₂capture process; this cooling of the flue gas advantageously reduces thesize and/or duty cycle of cooling units utilized in the processing ofhot flue gas prior to introduction to a CO₂ capture unit. Steam (190)produced in the reflux heater (185) may directed to the stripper (105),where it may be used to aid in the CO₂ removal process.

Another embodiment of a system of the inventive concept is shown in FIG.2. Rich solvent (200) from a CO₂ capture unit (not shown) is directed toa stripper (205). A semi-lean solvent (210) is collected from a pointbelow the packing and directed to a reboiler (220), where it is heated.Heat energy may be supplied to the reboiler (220) in the form of lowpressure steam (230). Such steam may, for example, be collected from theexhaust of a turbine. Examples of suitable turbines include, but are notlimited to, a low pressure turbine from a series of high, mid, and lowpressure turbines utilized for power generation and a turbine used topower a compressor. Utilization of such sources of low pressure steamadvantageously minimizes the impact on power generation.

At least a portion of the low pressure steam condenses in this process,generating a reboiler condensate (235), and transferring the resultingheat of condensation from the condensing steam to the solvent.Utilization of this phase change for energy transfer advantageouslyreduces exposure of the solvent to high temperatures, such as those thatare experienced when solvent is heated using high pressure steam, whichminimizes degradation of the solvent. This results in vaporization of aportion of the semi-lean solvent, and the resulting two phase solvent(225) is returned to the stripper (205). This releases stripping steamwithin the stripper (205), where the substantially CO₂ free lean solvent(240) is removed from a lower portion of the stripper (205) and may bedirected to a CO₂ capture unit.

In some embodiments of the inventive concept, the lean solvent (240) isremoved from the bottom of the stripper (205). Stripping steam risesthrough the stripper (205), carrying released CO₂ through the upper partof the stripper (205) as a CO₂ saturated stream (245). CO₂ may bereleased from other components of the CO₂ saturated stream (245) bycooling in a condenser (250), and subsequently separated from liquidcomponents in an accumulator (265). In typical overhead accumulator(265) configurations, product CO₂ (255) is collected from an upperportion and product condensate (260), condensate is collected from alower portion. This condensate (260) may be primarily water, but mayinclude amines or other compounds utilized in the capture of CO₂.

Condensate (260) may be distributed to one or more destinationprocesses, optionally with the aid of a pump (267). Embodiments of theinventive concept may include one or more valves and/or pump(s) and anassociated controller that permits control of the distribution or thecondensate (260) in order to optimize plant operations. In someembodiments of the inventive concept, at least a portion of thecondensate (260) can be directed to the stripper (205) as reflux (270).In other embodiments of the inventive concept, at least a portion of thecondensate (275) can be directed to other parts of the CO₂ captureprocess (not shown). In still other embodiments of the inventiveprocess, at least a portion of the condensate (280) can be directed toreflux heater (285). The reflux heater (285) may use the condensate(260) to generate steam (290) utilizing heat from a suitable source. Insuch an embodiment heat may be supplied to the reflux heater (285) bycondensate (235) produced by prior heat transfer in a reboiler (220).Heat transfer from the condensate (235) generates a sub-cooledcondensate (237). Steam (290) produced in the reflux heater (285) may bedirected to the stripper (205), where it may be used to aid in the CO₂removal process.

An embodiment of a method of the inventive concept is shown in FIG. 3.At least a portion of an upper product (310) obtained from a stripper(300) may be condensed in condenser (320) to produce a condensed stream.Part of this condensed stream from condenser (320) may be returned tothe stripper (300) as a reflux stream (330). Another part of thiscondensed stream may be provided to a heat exchanger (335) thattransfers heat from a heat transfer medium (340) to produce steam (350)that is returned to the stripper (300). The heat transfer medium may beflue gas, produced by an upstream boiler or other device and/or devicesas described above. Alternatively, the heat transfer medium may be acondensate from a reboiler. In some embodiments of the inventive conceptthe condensed stream may be separated into a CO₂ product (325) and acondensate stream (327), where the condensate stream forms at least partof the material that is provided to the heat exchanger (335) forproduction of steam (350).

Another embodiment of a method of the inventive concept is illustratedin FIG. 4. An upper product stream (410) and a solvent stream (420) areobtained from a stripper (400). At least a portion of the upper productstream (410) may be condensed in condenser (430) to produce a condensedstream. A portion of this condensed stream from condenser (430) may bereturned to the stripper (400) as a reflux stream (440). A secondportion of this condensed stream may be provided to a heat exchanger(450) to produce steam (470) that is returned to the stripper (400). Thesolvent stream (420) may be heated in a second heat exchanger (480)using a second heat transfer medium (460); the resulting cooled secondheat transfer medium (465) may in turn be utilized by the heat exchanger(450) to produce at least a portion of the steam (470) utilized by thestripper (400). The heat transfer medium (460) may be may be, forexample, a low pressure steam. In some embodiments of the inventiveconcept the condensed stream may be separated into a CO₂ product (435)and a condensate stream (437), where the condensate stream forms atleast part of the material that is provided to the heat exchanger (450)for production of steam (470).

In embodiments of the inventive concept where reboiler condensate (235)is used as a heating medium in a reflux heater (285), the condensate canreturn to the power plant colder in the current art, however, net steamdemand is reduced. Typical reductions in steam demand for the presentinvention may be around 6%. In the case of a power plant, embodiments ofthe inventive concept reduce the need for low pressure steam to heat thesolvent, which can advantageously increase the power output of thegenerator. This advantageously mitigates the impact of any retrofittingthat would be required for a low pressure steam turbine during theinstallation of a carbon capture plant utilizing an embodiment of theinventive concept.

As used herein, and unless the context dictates otherwise, the term“coupled to” is intended to include both direct coupling (in which twoelements that are coupled to each other contact each other) and indirectcoupling (in which at least one additional element is located betweenthe two elements). Therefore, the terms “coupled to” and “coupled with”are used synonymously.

It should be apparent to those skilled in the art that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. The inventive subjectmatter, therefore, is not to be restricted except in the scope of theappended claims. Moreover, in interpreting both the specification andthe claims, all terms should be interpreted in the broadest possiblemanner consistent with the context. In particular, the terms “comprises”and “comprising” should be interpreted as referring to elements,components, or steps in a non-exclusive manner, indicating that thereferenced elements, components, or steps may be present, or utilized,or combined with other elements, components, or steps that are notexpressly referenced. Where the specification claims refers to at leastone of something selected from the group consisting of A, B, C . . . andN, the text should be interpreted as requiring only one element from thegroup, not A plus N, or B plus N, etc.

What is claimed is:
 1. A method for reducing an energy requirement of aCO₂ capture process, comprising: condensing at least a portion of anupper product stream of a stripper to produce a condensed stream;feeding at least a first portion of the condensed stream to the stripperas a reflux stream; heating a second portion of the condensed stream ina heat exchanger via heat exchange contact with a heat transfer mediumto produce steam; feeding the steam to the stripper; withdrawing asolvent stream from the stripper; heating the solvent stream from thestripper in a reboiler to produce a reboiler stream, returning thereboiler stream to the stripper; and cooling and condensing at least aportion of a second heat transfer medium via heat exchange contact withthe solvent stream in the reboiler to produce a reboiler condensate,wherein the heat transfer medium comprises the reboiler condensate. 2.The method of claim 1, wherein the upper product stream comprises CO₂.3. The method of claim 2, wherein the upper product stream furthercomprises steam.
 4. The method of claim 1, wherein the stripper sconfigured to receive a CO₂-rich solvent stream.
 5. The method of claim1, wherein condensing at least the portion of the upper product streamcomprises introducing the upper product stream into a condenser.
 6. Themethod of claim 1, further comprising: separating at least a portion ofthe condensed stream to produce a CO₂ product stream and a condensatestream; and wherein the at least the portion of the condensed streamcomprises at least a portion of the condensate stream.
 7. The method ofclaim 6, wherein separating at least a portion of the condensed streamcomprises introducing the portion of the condensed stream into anaccumulator.
 8. A method for reducing an energy requirement of a CO₂capture process, comprising: condensing at least a portion of an upperproduct stream of a stripper to produce a condensed stream; feeding atleast a first portion of the condensed stream to the stripper as areflux stream; heating a second portion of the condensed stream in aheat exchanger via heat exchange contact with a heat transfer medium toproduce steam; and feeding the steam to the stripper; withdrawing asolvent stream from the stripper; heating the solvent stream from thestripper in a reboiler to produce a reboiler stream; returning thereboiler stream to the stripper, and cooling and condensing at least aportion of a second heat transfer medium via heat exchange contact withthe solvent stream in the reboiler to produce a reboiler condensate,wherein the second heat transfer medium comprises low pressure steam,and wherein the heat transfer medium comprises the reboiler condensate.9. The method of claim 8, wherein the upper product stream comprisesCO₂.
 10. The method of claim 9, wherein the upper product stream furthercomprises steam.
 11. The method of claim 8, wherein the stripper isconfigured to receive a CO₂-rich solvent stream.
 12. The method of claim8, wherein condensing at least the portion of the upper product streamcomprises introducing the upper product stream into a condenser.
 13. Themethod of claim 8, further comprising: separating at least a portion ofthe condensed stream to produce a CO₂ product stream and a condensatestream, wherein separating at least a portion of the condensed streamcomprises introducing the portion of the condensed stream into anaccumulator; and wherein the at least the portion of the condensedstream comprises at least a portion of the condensate stream.
 14. Themethod of claim 8, wherein the heat transfer medium comprises anupstream flue gas stream.
 15. The method of claim 1, wherein the heattransfer medium comprises an upstream flue gas stream.